Dressing mechanism for grinding wheels



' July 4, 1944.

DRESSING MECHANISM FOR GRINDING WHEELS Original Filed De c. 2, 1937 4 Sheets-Sheed 1 I l l l l l l 1 l %;owo j Era O7 Shae/erodwao gys l. J. SNADER 2,352,661

4 Sheets-Sheet 2 July 4, 1944. l. J. SN'ADER DRESSING MECHANISM FOR GRINDING WHEELS Original Filed Dec. 2, 1937 July 4, 1944. l. J. sNADER 2,352,661

- DRESSING MECHANISM FOR GRINDING WHEELS Original Filed De. 2," 1937 4 Sheets-Sheet 3 7 NvaN-rop 3 )"a C7 IS/7067916 (flTTOQugjS 4 July4, 1944.

I. J. SNADER DRESSING MECHANISM FOR GRINDING WHEELS Original Filed Dec. 2, 1957 4 Sheets-Sheet 4 (a u d n 5 rlu flou nmu wfi n u m 4 M m n 6 6 v 5 W 6 Wa Eu WWW? 6 4T 4 U wwm J2 H M J W M a x E a Patented July'4, 1944 Ira J. Snadcr, Detroit. Mich assigno'r to Ex- Cell-O Corporation, Detroit, Mich, a corporation of Michigan Original application December 2. 1931, Serial No. 177,693, now Patent No. 2,251,961, dated August 12, 1941. Divided and this application August 3, 1940, Serial No. 350,362 (Cl. 125-11) Claims.

The present invention relates to improvements in dressing mechanisms for grinding wheels,'and has particular reference to such mechanisms adapted for use in machine tools.

One of the objects of the invention is to provide a novel dressing mechanism which is conveniently and accurately adjustable to provide the grinding wheel selectively ,with different cutting contours adapted to grind various thread forms, such as U. S. standard, sharp V, acme and buttress.

Another object is to provide a new and improved dressing mechanism in which each dressing feed increment toward the grinding wheel is accompanied by a simultaneous compensatory feed increment of the wheel toward the work so as to compensate automatically for reduction in size of the wheel through dressing.

A further object resides in .the provision of a novel dressing mechanism which is adjustable relative to the grinding wheel and which may be quickly actuated into and out of dressing position without disturbing the dressing adjustment.

Other objects and advantages will become apparent as the description proceeds.

Figure 1 is a left end elevational view of a machine provided with a dressing mechanism embodying the features of my invention.

Fig. 2 is a fragmentary plan view on an en- Fig. 3 is a diagrammatic representation of the hydraulic circuits for the dressing mechanism.

Fig. 4 is a detail sectional view taken substantially along line 44 of Fig. 2.

Fig. 5 is a longitudinal vertical sectional vie taken substantially along line 55 of Fig. 6.

Fig. 6 is a transverse vertical sectional view taken substantially along line 66 of Fig. 5.

Fig. '7 is a fragmentary view of the dressing mechanism illustrated in Fig. 2.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The dressing mechanism constituting the exemplary embodiment of the present invention, although not limited in its broad aspects to any particular type of grinding machine, is especially suited, and is shown, applied to a machine adapted for grinding internal and external screw threads. Such a machine is disclosed in detail in my copending application, Serial No. 177,693, flied December 2, 1937, now Patent No. 2,251,961, of which the present application is a division. The machine comprises a base I having a front section 2 and a rearwardly extending section 3 at one end. The top of the base section 2 is formed with longitudinal ways 4 on'which a work carriage or work table 5 is suitably mounted for reciprocation. A headstock 8 is mounted on the work table 5 and is adapted t6 support a work blank (not shown) for rotation and for longitudinal reciprocation along the ways 4.

The top of the rear base section 3 is adapted to support a tool fixture I for cross feed and adjustment in a direction transversely of the ways 4. The fixture I has a power driven spindle 8 supporting a suitable grinding element or wheel v9 for cooperative engagement of the work. The

dressing mechanism of Figs. '1 to 5, identified generally by the numeral II) is mounted on the tool fixture I in position to shape and true the grinding wheel in accordance with the requirements of the work to be ground. For further details of the machine reference may be had to my aforesaid copending application.

The dressing mechanism III is mounted on a cross slide H for automatic adjustment transversely of the grinding wheel axis, and comprises a plurality of independently adjustable dressing units l2, l3 and It automatically operable to true the various faces-of the cutting contour of the external grinding wheel 9. v

In its preferred construction, the dressing mechanism It comprises a base bracket l5 mounted on the top of the cross slid II for movement therewith. A dresser slide I6 is mounted on the bracket I 5 for rectilinear feed transversely of the tool spindle 8, and is formed on the top with a plurality of arcuate guideways ll concentric about a vertical axis l8 in the central plane of the grinding wheel 9. The dressing units l2, l3 and H are mounted in the guideways I! for selective adjustment into different angular positions relative to the grinding wheel 9 depending on the form and character of the thread to be ground and hence the contour of. the wheel. It will be understood that the dressing units may be arranged for various thread forms, such as U. S. standard, sharp V, acme and modified butare shown arranged respectively to true the faces of a wheel contour having oppositely inclined side faces l9 and 28 and a peripheral face 2|.

Preferably, the dressing units l2, l3 and I4 are closely similar in construction so that a description of the unit l4 will suflice for all. This unit comprises a body bracket 22 (Fig. 4) havingan arcuate guideway 23 slidable on one of the guides A gear pinion 24 is journaled in the outer end of the bracket 22, and mesheswith a gear segment 25 on the slide l6 and concentric with the guide Two screws 26 are threaded through opposite ends oi an arm 21, rigid intermediate its ends with the pinion 24, for engagement with the bracket 22. The pinion 24 is adapted to be lifted out of engagement with the segment 25 to permit free movement of the bracket 22 along the guide I! for rough adjustment. Fine adjustment is obtained by turning the screws 26 oppositely to rotate the pinion 24 while in mesh with the segment 25. A suitable arcuate scale 28 is provided on the slide I6 to indicate the position of adjustment.

The body bracket 22 is adapted to be locked in position of adjustment bya gib block 29 which is disposed in a recess 39 in the guideway 23 for clamping engagement with the guide l1. and which is threaded on a screw 3| journaled in and extending to the front of the bracket 22 and there provided with a hand knob 32.

Fixed on the bracket 22 (as shown in the sectional view of the dressing unit I3) is a cylinder 33 which is, closed at one end by a plate 34 and has an elongated bearing sleeve 35 at the other end. A piston 36 is reciprocable in the cylinder 33 and is nonrotata'bly fixed on a rod 31 extending slidably through the sleeve 35. A pin 38 fixed in the cylinder 33 has a close sliding fit with the piston 36 to hold the latter against rotation in the cylinder 33. The outer end of the rod 31 is provided with a head 39 in which a suitable dressing tool 40 is secured for radial adjustment. Fluid under pressure is adapted to be supplied alternately from lines 4| and 42 (Fig. 3) opening to opposite ends of the cylinder 33 to reciprocate the piston 36 and thereby move the tool 40 in a dressing cut across theintended face of the grinding wheel 9.

The dresser slide l6 may be fed either manually, or automatically by hydraulic means once for each reciprocation of the work table 5. The feed means (see Figs. and 6) comprises a screw 43 rotatably anchored against endwise movement in antifriction bearings 44 in the base bracket. l5, and extending in threaded engagement with a fixed nut 45 on the underside of the slide l6. A worm wheel 46 is fixed on the screw 43 and mesheswith a worm 41 on a transverse shaft 48 supported in antifriction bearings 49 in the side of the bracket I5. The outer end of the shaft 49 extends through a housing 58, and is provided with a hand wheel 5|. A, ratchet wheel 52 is fixed on the shaft 48 within the housing 50, and is adapted for engagement by a pawl 53 pivotal on the upper end of a vertical lever 54. The lower end ofv the lever 54 is rigid with a gear segment 55 which is freely rotatable on the shaft 48, and which meshes with a longitudinal gear rack 56 on a piston rod 51. The rod 51 is connected to a piston 58 reciprocable in a cylinder 59 mounted within the bracket l5. Fluid pressure is adapted to be supplied alternately through lines 69 and 6| to opposite ends of the cylinder 59 to eifect reciprocation of the pawl 53. The length of the automatic stroke of the pawl 53 and hence the dresser feed incredusting the cross slide ment is subject to adiustment by means of a stop screw 62 which is adjustably threaded through one wall of the bracket l5 and limits the outward movement of the piston rod 51.

A hand lever 63 is journaled in one wall of the bracket I5, and has an arm 63 adapted for engagement with a pin 64 on the pawl 53 to lift the latter out of engagement with the ratchet wheel 52 when it is desired to feed the slide [6 manually, for example, to retract the slide for the purpose of mounting a new grinding wheel 9.

For each dressing feed increment, a like approach feed increment is imparted to the tool cross slide II to compensate for the reduced diameter of the grinding wheel 9. To this end, a second cylinder 65 is connected in parallel with the cylinder 59 across the fluid lines and 6|. A piston 66 is reciprocable in the cylinder 65, the two pistons 58 and 66 being operable simultaneously. The piston 66 is operatively. connected through a feed mechanism to a worm 61 for ad- This feed mechanism may be the same as the feed mechanism actuated by the piston 53 for rotatingthe worm 4! in the feed drive for the dressing mechanism, and hence is not separately shown in detail.

The worm 61 meshes with a worm wheel 66 secured to a nut 69. This nut is rotatably confined by a plate 10 in a bracket 1| rigidly secured to the under side of the cross slide. A cross feed screw 12 is threaded through the nut 69 and is adapted for connection to suitable drive means (not shown). nism I9 is idle, the worm 61 serves to hold the nut 69 against rotation so that actuation of the :crew 12 will effect feed adjustment of the cross sl de H and the grinding wheel 9 thereon. When the piston 58 is actuated to impart a dressing feed increment to the slide |5, the worm 61 is operated to rotate the nut 69 and thereby impart a like increment to the tool slide II to compcnsate for the stock to be removed from the V grinding wheel 9 in the dressing operation.

Hydraulic circuit The lines 60 and 6| to the dresser feed cylinder 59 and the compensatory cross feed cylinder are adapted to be reversibly connected, through a hand valve 13 directly to a fluid pressure line 14 and an exhaust line 15. When not in use, the valve 13 is held in position by an internal spring (not shown).

The three cylinders 33 for the dressing units I2, l3 and I4 are connected in series for successive operation to the lines 4| and 42.- More particularly, the line 4| opens to one end of the first cylinder 33. A line 16 adapted to be opened by the associated piston 36 when the latter reaches the end of its stroke in one direction is connected through a bypass check valve 11 to the line 4| and opens to the inner end of the second cylinder 33. Another line 18 adapted to be opened by the associated piston 36 when the latter reaches the outer end of its stroke is connected through a bypass check valve 19 to the line 16 and opens to the outer end of the third cylinder 33. Similarly, the line 42 opens to the inner end of the third cylinder 33. A, line 89 adapted to be opened by the third piston 36 when the latter reaches its outermost position is connected through a bypass check valve 8| to the line 42 and opens to the outer end of the second cylinder 33. A line 82 adapted to be opened by the second piston 36 when the latter reaches its innermost position is'connected through a by- When the dressing mechapass check valve II to the line 80 and opens to the outer end of the first cylinder 33. All ofthe cylinder lines open to the cylinders at the top so as to permit removal of air.

It will be evident that when pressure fluid issupplied to the line H, the first tool 40 will dress one inclined face is, then the second tool 40 will dress the peripheral face 2 I, and finally the third tool 40 will dress the other inclined face 20. The fluid from the other ends of the cylinders will exhaust freely through an open exhaust connection common to all of the cylinders and comprising the line 82, the check valve 83, the line IO and the check valve 8| to the line 42. When hand valve II to a fluid pressure line 88 andthe exhaust line 15'.

The hand valve 84, which is used while setting the dressing mechanism Iii to a new grinding wheel 8, is normally urged into one position by spring means (not shown) to maintain the tools when not in use away from the wheel. Similarly, the valve 81 is normally held in one position by pressure fluid from the line 88.

ing a reciprocatory tool and a hydraulic motor for reciprocating said tool, hydraulic means for reversibly supplying fluid under pressure successively to the motors of said units to reciprocate said tools in timed sequence, hydraulically operated means for feedingsaid slide toward said spindle, and hydraulically operated means operable in synchronism with said last mentioned means to move said support in timed relation to the movement of said slide.

2. A dressing mechanism comprising, incombination, a support, an arcuate guideway on said support and formed with a concentric gear segment, a bracket slidably mounted on said guideway, a pinion joumaled in said bracket and meshing with said segment, a transverse lever rigid intermediate its ends with said pinion, adjusting screws threaded through opposite ends of said lever into abutting relation with said bracket and being oppositely adjustable to rotate said pinion and being relatively adjustable to secure said pinion in position of adjustment, releasable clamp means for securing said bracket ii -position of adjustment, a cylinder rigid with said bracket, a piston reciprocable in said cylinder and having a piston rod extending therefrom, and a dressing tool adjustably mounted on the outer end of An adjustable oriflce valve 8Q is interposed in the exhaust line 15 at the outlet side of the valve IT to meter the fluid discharged from the vanced into operative relation to the wheel 9 by repeatedly reversing the hand valve 13. Operation of the dressing units l2, l3 and I4 is effected by the hand valve 81 at the front of the machine or the hand valve 84 at the rear of the machine, and the rate of dressing tool movement is under the control of the adjustable orifice 89.

Forredressing the wheel 9 to compensate for wear or to redefine the cutting contour, the valve 13 is actuated to advance the dressing mechanism II to the desired extent toward the wheel, and then the dressing units I2, I! and I are actuated as before. An equal feed is simultaneously imparted to the slide ii to compensate for the rerocable dressing tool and a reversible hydraulic v duced diameter of the wheel 9, and thereby maintain the initial gauge setting.

said rod.

3. In a machine tool, in combination, a base, a grinding wheel operatively mounted on said base, wheel dresser means on said base including a plurality of dresser units each having a reciprocable dressing tool and a hydraulicmotor for driving said tool, and hydraulic means for supplying fluid under pressure to each of said motors in succession including means controlled by an actuated motor for connecting the next motor to be actuated with the fluid supply.

4. In a machine tool, in combination, a base, a grinding wheel operatively mounted on said base, wheel dresser means on said base including a plurality of dresser units each having a recipmotor for driving said tool, and hydraulic means for supplying fluid under pressure reversibly to each of said motors in succession including means controlled by anactuated motor for connecting the next motor to be actuated with the fluid supply.

5. In a machine tool, in combination, a base, a grinding wheel operatively mounted on said base, wheel dresser means on said base including a plurality of dresser units each having a reciprocable dressing tool and a reversible hydraulic motor for driving said tool, and hydraulic means for supplying fluid under pressure reversibly to each of said motors in succession including means controlled by an actuated motor for connecting the next motor to be actuated with the fluid supply, said motors in either direction of operation discharging to a common exhaust line, and an adjustable oriflce in said exhaust line for controlling the rate of movement of said tools.

IRA J. SNADER. 

